A Waihi man is leading a group of local homeowners in planning legal action against a real estate agency which they claim did not tell them their properties were in an area that had a permit for gold mining.

But the agency says it has done nothing wrong.

Rob and Angela McCarthy have spent more than $400,000 developing their new home since they bought their Mataura Rd property in 2010 for $660,000.

At the time of sale they say they did not know Newmont Waihi Gold had already signalled its permit to mine below the property.

Mr McCarthy, 58, claims that he was not told there were any issues with mining when he asked the PGG Wrightson agent directly. He bought the property despite not obtaining a Lim report or seeking further advice from the Hauraki District Council or other real estate agents.

"I have known the realtor for quite a long period of time and have played golf with him and have talked real estate with him for most of his real estate career and asked him the important questions for which he should have had the correct answer to."

Newmont Waihi Gold has since sought resource consent for its proposed Correnso mine, which would run underneath Mr McCarthy's land.

Mr McCarthy, a licensed real estate agent, said the value of his property has been reduced.

"I've been selling real estate for 28 years and I was a teacher prior to that, and all of a sudden the value of my assets has been affected ... I'm not impressed."

The McCarthys are one of three parties involved in two separate efforts to seek redress.

Their lawyer, Auckland barrister Grant Collecutt, notified lawyers at PGG Wrightson about the complaint late last year and is filing a complaint with the Real Estate Agents Authority.

He expects to launch civil proceedings in the High Court but is seeking more homebuyers for the claim. The case had the potential to become a class action with potentially dozens of homes and other real estate agencies involved.

Stuart Cooper, general manager of real estate at PGG Wrightson, said a complaint from Mr McCarthy was received last November and he expects to discuss the matter with him at "some time in the new year".

He said an internal investigation revealed no wrongdoing by the agent concerned.

"Certainly as far as the complaint was made we don't believe that any of our people have done any wrongdoing at all," he said.

Mr McCarthy described the action as a "heavyweight complaint" that could eventually involve millions of dollars.

"I think a lot of people don't know where they stand legally and are scratching their heads ... they don't know they were supposed to have been told," Mr McCarthy said.

Helen O'Sullivan, the Real Estate Institute's chief executive, said the existence of a mining permit was material to prospective purchasers and should "definitely be disclosed by an agent".

"The key question would always be whether a specific consent existed at the time of a transaction and to what extent licensees could be expected to have known of the consent and its boundaries at the time that a specific transaction took place."